Cytarabine ocfosfate (hereafter referred to as COP) is known in U.S. Pat. Nos. 4,812,560 and 5,049,663, etc. Capsules of arabinofuranosylcytosine-5'-phosphate (Ara-CMP) are described in U.S. Pat. No. 4,542,021. In the pharmaceutical preparations, potato starch and lactose are added to prepare the capsules.
Where it is attempted to prepare COP into oral preparations such as capsules, etc. by adding starch and lactose thereto as in a conventional manner, the starch and lactose should be added to COP in considerably large amounts; where one needs to take COP in a dose necessary for treatment, the size of preparations so increases due to poor dispersibility that one can orally take the COP preparations only with difficulty. Further in order to disintegrate capsules satisfactorily, starch and lactose must be added in large quantities so that stability of COP is deteriorated and its decomposition products are formed; in this case, problems of decreased content of COP, etc. encounter. In addition, COP has a property that is extremely sparingly soluble in an acidic solution having pH below 4. A mere tabletting by compressing COP or encapsulation of COP results in a disadvantage that disintegration in an acidic solution is extremely retarded. Taking the physiological pH in the stomach into account, it is desired to provide pharmaceutical preparations capable of being readily disintegrated even in an acidic region.
An object of the present invention is to provide hard capsules which are excellent in stability of COP and do not impair their disintegrating property even in an acidic solution.